Nitrogen-based plant food.
Does a nitrogen-based plant food affect all bulbs this way or only Cala Lillies?
Nitrogen promotes green leafy growth in all plants. In excess, this growth will be at the expense of flowers. Obviously, plants need some nitrogen; it is the one major nutrient that passes through soil the quickest. Also, a fertilizer with lots of phosphorus and potassium can cause problems. A soil test is the best way to determine the nutrient needs of the soil in your garden. Without one, you are traveling blindly and at the mercy of fertilizer adds/product labels. Good cultural practices such as topdressing with 2 inches of compost, may be all that is necessary in healthy soil that isn't sandy.